Transcription of Electric Motor Selection and Sizing - me.ua.edu
1 Electric Motor Selection and Sizing Electric Motor Selection Type Selection - DC Motor Two basic decisions to make: DC motors are typically used when What type of Motor is needed? low- low-cost, _____ is advantageous but precise speed regulation not required DC Motor ? AC Motor ? starting torque required _____. than running torque Oncetype of Motor is selected, what size brief overloads OK, since Motor has time to cool Motor is required? frequent start/stop cycles, reversing, or closed- closed- loop positioning required Type Selection - AC Motor Brainstorming Scenario AC motors are typically used when Your group has been hired to select motors for low- low-cost, _____ is advantageous various applications and products gearing required to deliver speeds that are Possibilities include: significantly less than 1200 RPM DC Motor (w/brushes). starting torque _____ running torque Brushless DC Motor briefperiods of high running torque frequently Split phase AC Motor handled by flywheels Permanent Split Capacitor (PSC) AC Motor available access to AC power Shaded pole AC Motor Universal Motor In- In-Class Exercise Motor Sizing #1.
2 Match one of the 6 different types of motors to The major constraint on all Motor operation these applications & justify your Selection : is thermal in nature. Electric knife for carving turkey Electrical Power = Power Dissipated + Mechanical Power constant speed conveyor belt with frequent (Input) (as heat) (useful output). start/stops power window drive in auto The heat a DC Motor must dissipate can be fan in indoor HVAC unit calculated: industrial robot used in painting applications Electric Motor Selection and Sizing Motor Sizing #2 Motor Sizing #3. Each specific Electric Motor will have its own Each type of load will have its own torque- torque- characteristic torque-speed curve speed requirements PMDC Motor Viscous Friction AC Motor Pumps and Fans ( speed2). Torque, . Torque, Constant Universal Motor Speed, . Speed, . Motor Sizing #4 DC Motor Ratings Operating point occurs at intersection of Motor DC motors are rated at a single speed and and load speed/torque curves torque In most cases, the Motor can operate at this Torque, Torque.
3 AC Motor DC Motor point _____. Constant temperature rating will not be exceeded DC motors rated with _____. Pump DC motors are typically used at about _____ of rated speed Speed, Speed, about _____ of rated torque AC Motor Ratings DC Motor Selection Example A 12 volt battery- battery-powered DC Motor is used on a AC motors are also rated at a single speed child's toy Jeep and horsepower What power (in watts and hp) is required for this 3450, 1725, 1140, 850 RPM are common application? Hint ignore acceleration AC Motor can operate here continuously Which Motor should be selected from the spec sheet provided for the application? temperature rating will not be exceeded AC motors are typically used at V=3 ft/sec about _____ of rated torque/power Total mass much lower efficiency if Motor is _____. m=40 kg ( over- ( over-rated ). 5o)
